(一)现在分词和过去分词的区别
(1)在语态上现在分词表示主动的意思，表示它所修饰的人或物的行为;及物动词的过去分词表示被动的意思，表示它所修饰的人或物是动作的承受者。换言之，现在分词是它修饰的成分所作出的动作，过去分词是它修饰的成分所承受的动作。例如：
convincing facts 有说服力的事实 / convinced audience 被说服了的听众
the exploiting class 剥削阶级 / the exploited class被剥削阶级
a frightening dog一条让人害怕的狗 / a frightened dog一条被吓坏了的狗
driving gears主动齿轮 / driven gears从动齿轮
(2)在时间上，现在分词往往表示动作正在进行，过去分词表示动作已完成。例如：
the rising sun (正在升起的太阳) / the risen sun(升起的太阳)
the falling rain(正在下的雨)/ the fallen leaves(落下的树叶)
stolen money(被盗的钱/偷来的钱)/ill-gotten wealth(不义之财)
a high-flying kite(高飞的风筝)
再看一些例子：
boiling water 沸腾的水/boiled water 开水/developing countries 发展中国家/developed countries 发达国家/an exciting story 令人激动的故事/ excited people 激动的人们
(3)做表语时的不同。现在分词做表语表示主语所具有的特征，意思是“令人如何”。过去分词多表示主语所处的状态，意思是“感到如何”。例如：
His lecture is disappointing. I’m disappointed. 他的演讲令人失望。我感到失望。
We are surprised to hear the news. The news is surprising. 我们听到那消息吃了一惊。那消息令人吃惊。
The situation is encouraging. We’re encouraged. 形式使人鼓舞。我们感到鼓舞。
常用的还有：amusing/amused，astonishing/astonished，disappointing/disappointed，exciting/excited，frightening/frightened，interesting interested，moving/moved， relaxing/relaxed，satisfying/satisfied，shocking/shocked，surprising/surprised，terrifying/terrified，tiring/tired，worrying/worried等等。
(4)做状语的区别，分词短语在句中可做时间、原因、方式、伴随状语。现在分词的动作和谓语动作同时或几乎同时发生、意思是主动的。而过去分词的动作在谓语动作之前发生、意思是被动的。例如：
Seeing nobody at home, she decided to leave them a note. 看到没人在家，她决定给他们留个条。(主动意义，几乎同时)
The secretary worked late into the night, preparing a speech for the president. 秘书工作到晚上很晚，给总统准备一篇演说。(主动意义，同时)
Tired of the noise, he closed the window. 对噪音感到厌烦，所以他把窗户关上。(被动意义，在谓语之前)
Deeply moved, she thanked me again and again. 她深深地受了感动，再三谢我。(被动意义，在谓语之前)
Persuade by my mother, she gladly went there alone. 在我母亲劝说下，她才高兴地独自去那里。(被动意义，在谓语之前)
如果现在分词的动作在谓语动作之前发生，现在分词要用完成形式，但意思仍然是主动的。例如：
Having watered the vegetables, they began to pick up the Apples.=After they had watered the vegetables, they began to pick up the apples.他们浇完了蔬菜之后就开始摘苹果。
Having finished the work, he packed his tools and left. 完工后，他收拾起工具走了。
分词做状语时，前面可用连词或介词。例如：
After eating my dinner quickly, I went to see Jim off. 我赶快吃过晚饭就去给吉姆送行。
Though built before the Second World War, the engine is still in good condition. 尽管是在二战以前建的，这引擎仍然处于良好状态。
Unless paying by credit card, please pay in cash. 如果不用信用卡付款，请用现金付。
Tom will never do this unless compelled. 汤姆永远也不会干这种事，除非被逼无奈。
She’s been quite different since coming back from America. 从美国回来后，她大变了。
(二)用法
1.作定语。作定语的分词通常放在被修饰的名词之前。如果被修饰的词是something，anything，everything，nothing等，则分词放在这些词之后。分词短语通常放在被修饰的名词之后。例如：
This is an interesting book. (=This is a book. It is interesting. )这是一本有趣的书。
There is something interesting in the news. (=There is something in the news. It is interesting.)消息中有些有趣的事。
The man sitting by the window is our math teacher. (=The man who is sitting by the window is our math teacher.)靠窗户坐着的那个人是我们的数学老师。
The machine run by the old worker is made in Shanghai. (=The machine that is run by the old worker is made in Shanghai.)那位老工人开的机器是上海造的。
Most of students singing were girls. (=Most of the students who were singing…) 唱歌的学生多数是女生。
Many of the villagers questioned refused to answer. (=Many of the villagers who were questioned…) 被问的许多村里人都拒绝。
注意：(1)分词作定语与动名词作定语的区别：分词和它所修饰的名词有逻辑上的主、谓关系。动名词则没有这种关系，而表示它所修饰的词的用途或有关动作。(2)现在分词作定语时，它表示动作正在进行或与谓语动词所表示的动作同时发生(或差不多同时发生)。(3)be的现在分词being不能用作定语(可用作状语或被动语态中的助动词)。表示这种概念时，也用主从复合句结构。
2、作状语。分词和分词短语作状语时，可以表示时间、原因、行为方式等意义。表示时间和原因的分词短语相当于对应的状语从句。例如：
Seeing the teacher entering the room, the students stood up. (=When the students saw the teacher entering the room. They stood up.)学生们看见老师走进房间，都站了起来。 (时间)
Heated，the Metal expands. (=The metal expands if /when it is heated.)金属受热而膨胀。(条件、时间)
Being excited, I couldn’t go to sleep.(=As I was excited, I couldn’t go to sleep.)我兴奋得睡不着觉。(原因)
Being a student, he was interested in sports. (=As he was a student, he was interested in sports.)他是个学生，所以对体育运动感兴趣。(原因)
Inspired by Dr.Yang’s speech, Li Hua and his classmates decided to study physics harder. (=As they were inspired by Dr.Yang’s speech, Li Hua and his classmates decided to study physics harder。)李华和他的同学们受到杨博士讲话的鼓舞，决定更加努力学习物理。 (原因)
The children went away laughing. (=The children went away.They laughed as they went.) 孩子们笑着走开了。(行为方式)
The professor stood there, surrounded by many students. (=The professor stood there. He was surrounded by many students.) 教授站在那里，许多学生围着他。(行为方式)
While reading the newspaper, father nodded from time to time. (=While he was reading the newspaper, father nodded from time to time.) 看报时，父亲不时地点头。(时间)(分词前，可加表示时间的连词while或when。)
3、作宾语补足语。例如：
Can you get the machine going again? 你能使机器再动起来吗?
You should have your hair cut. 你该理发了。
I saw him coming last night. 我昨天晚上看见他来了。
4、作表语。例如：
The film is very moving. 这部影片很感人。
Your homework is well done. 你的作业做得好。
The visitors looked surprised. 参观者看上去很惊讶。
The boys were seen walking on the grass. 有人看见孩子们在草地上散步。
5、作句子独立成分(分词有自己的逻辑主语时，称为独立主格结构) 。例如：
Flags flying, the army men marched in the streets. 旗帜飘扬，军队在街上行进。
All his ribs broken, he lay half dead. 他的肋骨全部折断，半死不活地躺着。
分词(短语)作状语时，其逻辑主语必须与句子的主语一致。如果不一致，必须用独立主格结构来表示，也就是在分词前面加上它的逻辑主语。
My wife had a long talk with Sally, explaining why she didn’t want the children to play together我妻子与莎莉谈了很长时间，解释她为什么不想让孩子们在一起玩。(现在分词explaining是句子主语my wife做的动作，它们之间是主动关系)
Given more attention, the trees could have grown better. 如果对这些树多关心一些，它们本来会长得更好。(过去分词given表示的动作是句子主语the trees承受的动作，它们之间是被动关系)
We explored the caves, Peter acting as guide. 我们到那山洞探险，彼得做向导。 (独立主格)
The train having gone, we had to wait another day. 分词短语做状语时，前面可以加上连词或介词，但是分词短语和句子之间不能用并列连词(如but，and)，因为并列连词接的是两个并列成分，
而分词短语只是全句的一个状语部分。分词和主句之间可用逗号。例如：
误：Having been told many times, but he still couldn’t understand it.
正：He was told many times, but he still couldn’t understand it.
注意：(1)分词作状语时，逻辑主语即句子的主语;否则要用从句或独立主格结构来表示。例如：
Looking out of the window, I saw lots of people there.(=When I looked out of the window, I saw lots of people there.)
我往窗外一看，看见那儿有许多人。 (looking out of the window的逻辑主语，就是句子的主语I。)
(2)在see，hear，watch，notice等动词后，用动词不定式作宾语补语，通常表示(强调)动作从开始到结束的全过程。如果用现在分词作宾语补语，则通常表示动作正在进行。例如：
We sat two hours and watched the teacher make the experiment. 我们坐了两个小时，看老师做实验。(两小时一直在看老师做实验)
We passed by the classroom and saw the teacher making the experiment. 我们走过教室，看见老师在做实验。(只是在走过教宰的一刹那间，看见老师正存做实验)
I saw him enter the room, unlock a drawer, take out a document, photograph it and put it back. 我看见他走进房间，打开抽屉，拿出一份文件，拍了照又放回去(表示一个接一个的一系列动作的全过程时，用动词不定式。
I noticed them sitting in the corner and talking about something secret. 我注意到他们坐在角落里在谈论什么秘密事儿。 (表示几个同时正在进行的动作，用现在分词)
(3)在“have+宾语+分词”的结构中，用现在分词或过去分词表示的意义不同。在“have+宾语+现在分词”的结构中，现在分词所表示的动作往往是主体让(叫、使、听任、允许)客体做的，或使客体保持或处于某种状态。例如：
He had the fire burning day and night. 他让火日夜燃烧着。
Father had me swimming the whole summer vacation. 父亲让我整个署假天天游泳。
在“have(get)+宾语+过去分词”的结构中，过去分词所表示的动作往往是别人做的或与主体的意志无关。例如：
Mary had her dress washed. 玛丽叫别人洗了她的衣服。(衣服是被洗)
had his legs broken. 他的腿骨折断了。(表示与主体意志无关的客观遭遇)
I had my watch stolen yesterday. 昨天我的表被人偷了。(表是被偷)
They had Jack beaten. 他们叫人打了杰克。(Jack是被打)
(4)分词作表语时，现在分词有“主动”、“进行”、“使”等意义;过去分词有“被动”、“完成”“受”、“感到…”等意义。例如：
The story is interesting. 这个故事很有意思。(故事使人感兴趣)
He is interested in dancing. 他对舞蹈感兴趣。
(5)谓语动词的现在进行时和作表语的现在分词形式相同;被动语态动词谓语和作表语的过去分词形式相同，但两者的意思不一样。
试比较：
They are moving their bed.他们正在搬床。 (are moving是谓语，表示主体的动作)
The story is very moving.这个故事很感人。 (moving是表语，表示主体的特征)
Her homework was done by her sister.她的作业是她姐姐做的。 (was done是谓语动词被动语态)
Her homework is well done.她的作业做得很好。( done是表语)
(6)generally speaking(一般地说)，roughly speaking(粗略地说)，strictly speaking(严格地说)等现在分词结构都是习惯用语，在句子中作插入语。例如：
Generally speaking, a footballer of 20 is better than one of 40。
一般地说，二十岁的足球队员比四十岁的强。
(7)分词短语的逻辑主语就是句子的主语，而独立结构的逻辑主语和句子的主语是不同的。例如：
The last bus having gone, we had to walk home.
末班公共汽车已开走了，我们只好走路回家。
(三)分词的时态和语态
过去分词可以表示“被动”和“完成”等意义，因此没有时态和语态方面的形式变化。下面谈一下现在分词的时态和语态。
1.现在分词的完成式(having+过去分词)表示的动作发生在谓语动词所表示的动作之前或两个动作在时间上有一定的间隔。例如：
Having written the letter, John went to the post office.
(=After he had written the letter, John went to the post office.
约翰写完信后，就去邮局了。
Having lived in Beijing for years, Lao Wang knows the city quite well.
(=As he has lived in Beijing for years, Lao Wang knows the city quite well.)
老王在北京住了多年，所以对这个城市很熟悉。
Having drunk two glasses of water, Xiao Ma felt a little better.
(=After he had drunk two glasses of water Xiao Ma felt a little better.)
小马喝了两杯水，感觉好一些了。
一般式和完成式现在分词都可以表示先后接连发生的动作。在可能引起误解的场合应该用完成式现在分词表示先发生的动作。例如：
Opening the drawer, he took out his wallet.
(=He opened the drawer and took out his wallet.)
他打开抽屉，拿出钱包。
Coming into the room, he put down his bag.
(=he came into the room and put down his bag.)
他走进房间，放下提包。
Having brushed his teeth, Mr. Brown came downstairs for breakfast.
布朗先生刷过牙，就下楼来吃早饭。
(此句如写成:Brushing his teeth, Mr. Brown came downstairs for breakfast.可能指“边刷牙，边下楼’。)
2.现在分词的被动语态(being +过去分词)通常表示“正在被…”的意思。如强调现在分词表示的动作发生在谓语动词所表示的动作之前时，可用现在分词被动语态的完成式(having + been +过去分词)。例如：
The bridge being built will be completed next month. 正在修建的那座桥将于下月完成。
Having been kept out of the room about half an hour for his returning late, Tom was let in. 汤姆回来晚了，所以被关在门外半小时左右才让他进去。